The present invention relates, in general, to an air purifying cartridge for respirators of the type containing a chemical that releases oxygen under the action of carbon dioxide and moisture and, more particularly, to an air purifying apparatus for purifying expiratory air which contains a chemical, such as potassium perioxide, arranged in layers and separated by partitions within a housing.
Air purifying cartridges, in which oxygen is released from a filling material when expiratory air having a carbon dioxide portion and moisture is introduced, depend, with respect to their efficacy and durability in a warm environment, on the guidance of the expiratory air which is to be regenerated inside the air purifying cartridge as well as on the dissipation of heat, taken into the pastiness and coagulation of the filling material.
A known air purifying cartridge having a circular to oval cross-section contains potassium peroxide as the filling material in layers which are separated from each other by partitions. The supply of the respiratory air is effected through an axially arranged central tube which extends to the outside of the cartridge through a cover.
The central tube has bores distributed over the circumference between the intermediate screens through which a connection is established between the respective layers and the central tube. The expiratory air flows through the filling material within the cartridge from a space above the first layer into a space beyond the last layer. A partial current of this treated respiratory air flows through the tube bores into the central tube and combines there with the respiratory air that has entered the tube through bores communicating with the other layers and through an inlet to the central tube.
The air purifying cartridge can also be used in the opposite direction, that is, with the inflow directed through the central tube and the outflow through a connecting socket in the cover. In the first layers, a higher velocity of flow of the expiratory air having the higher carbon dioxide and moisture content, and in the following layers, a lower velocity of the expiratory air having a lower CO.sub.2 and moisture content leads to an effective utilization of the filling material. The use of this cartridge is limited where a prolonged period of use is desired by the pastiness and thus coagulation of the filling material which develops after a certain period of use. The pastiness is enhanced by the higher temperature of a warm environment. The coagulation makes further use impossible due to increased flow resistance. No reasonable extension of the time of use can be achieved by increasing the amount of the filling material. Measures must be taken to eliminate the heat and to account for the pastiness.
In another air purifying cartridge in which the filling material is arranged in layers separated by partitions, the partitions are suspended as concentric cylindrical screens. These are sealed at the end faces with tight closures. The upper end face has a central opening, however, leading to the inner cylindrical screen. A space between the outer cylindrical screen and the housing wall serves as a guide for the gas. The expiratory air to be regenerated enters through the opening and passes radially through the inner cylindrical screen to the outside through the respective layers of filling material and arrives in the aforesaid space where it accumulates and it is exhausted at the bottom. After passing through a cooler suspended on the lower end face and a breathing bag, it is again fed to the user. This cartridge does not have any means to prevent coagulation of the filling material. The usage time is thus limited just as in the previously described air purifying cartridge.